Contra Costa County Municipal Code Ch. 914-6 Open Channels and Ditches

Article 914-6.2 Earth and Lined Channels

Maximum design velocities for natural or improved earth channels shall be those specified by a licensed soil engineer in the soil report. The calculations shall be based upon the United States Department of Agriculture, Soil Conservation Service Tractive Force Method, or an alternative method approved by the public works department.

(Ords. 89-28, 78-5).

Minimum velocities at design capacity for earth channels shall be three feet per second.

(Ords. 89-28, 78-5).

Side slopes for improved earth channels shall be those specified by a licensed soil engineer, but in no instance shall side slopes be steeper than two horizontal to one vertical.

(Ords. 89-28, 78-5).

Side slopes for lined channels shall be those specified by a licensed engineer and shall be based upon the data contained in a soil report prepared by a licensed soil engineer. The engineering calculations shall also indicate the structural integrity of the lining and any needed subdrainage.

(Ords. 89-28, 78-5).

Where the outlet velocity from a lined channel exceeds the maximum allowable velocity for the earth channel receiving the flow, suitable protective works shall be constructed to dissipate the flow. At a minimum, the outlet end of the lined channel shall be protected by a cutoff wall and the placement of loose riprap. The protective works shall be those specified by a licensed engineer and shall be based on engineering calculations of allowable flow velocities.

(Ords. 89-28, 78-5).

Article 914-6.4. Roadside Ditches

No concentrated flow of storm waters from a subdivision shall be discharged into a roadside ditch.

(Ords. 89-28, 78-5).

Roadside ditch sections shall be subject to the approval of the public works department as to shape, size gradient, lining and location within the road right-of-way, and shall have the required hydraulic capacity.

(Ords. 89-28, 78-5).

Roadside ditches and gutters shall be provided to carry the drainage from the road and tributary lands without damage to the roadbed or abutting property.

(Ords. 89-28, 78-5).

The maximum gradient for earth roadside ditches shall not exceed four percent, nor be less than one percent. The minimum gradient for lined roadside ditches shall not be less than one percent.

(Ords. 89-28, 78-5).